One of my professors used to smoke cigars (the Tuscan cheap ones) and he used to steal a moment during recess, having a puff in the 5-men football pitch (you could still smoke there, those days) and then getting the un-smoked part of the cigar in its paper box, and this in his breast pocket. Once, halfway through a physics theorem and a disequation, we begin to smell something funny- yes, you got it. It was the cigar, not having being properly put off, burning through the jacket
